3D Systems and Stratasys have done well lately but that can change in a hurry. Investors would be wise to use caution with them, Cramer advises.

Cramer said he would be cautious about investing in 3D Systems (DDD) , whose stock surged Monday after a surprising top- and bottom-line earnings beat. But Tuesday, shares are down 13% after analysts at JPMorgan poured cold water on the stock.

Analysts downgraded 3D Systems to underweight from sell, slapped on a $10 price target and are leery of the company's sales visibility. The stock's 66% year-to-date rally (before Tuesday's decline) is a bit too enthusiastic, they said. Shares recently traded at $12.56.

He also said investors should be careful about investing in 3D's competitor Stratasys (SSYS) .

Maybe the bloom is off the rose and 3-D printing is "just not as big as people think," Cramer wondered. He said that while it was good 3D's shares bounced, investors should still be careful if they are considering investing in either company, he concluded.

At the time of publication, Cramer's Action Alerts PLUS had no position in companies mentioned.